| 摘要 |
PROBLEM TO BE SOLVED: To prevent a stepping motor from rotating over a restricted position by controlling the rotational speed of the motor so as to be lowered when the stepping motor has rotated to the restricted position on the basis of the number of step driving. SOLUTION: With the start of hot water supply, the temperature detected by a temperature sensor 14 and a set temperature are compared. When the detected temperature is lower than the set temperature, a controller 20 controls the rotation of a stepping motor 13 to rotate a rotary plate 37 toward the direction of 0 degree, thereby decreasing a bypass rate. In a conversed case, the rotary plate 37 is rotated toward the direction of 300 degree to increase the bypass rate. Subsequently, the operational conditions of limit switches 34, 35 are read out. When the switch is on, the motor 13 is regarded to be in a restricted position and the rotation is stopped. This process is repeated until hot water supply is stopped. Thus mixture control of hot and cold water is conducted according to the rotating position of the motor 13. As a result, the number of reading out of the limit switches 34, 35 in a detection zone of the restricted positions is increased to surely stop the rotation of the motor 13 within a range of the restricted positions, thereby preventing overrun.
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